The firm, which is part of the £180m turnover JRL Group, will manage the construction of the 161 flats under a £34m contract with joint venture developer Stanhope/Schroders.
These will be arranged over two high-rise blocks, 22 storeys and 9 storeys, accommodating a mixture of one and two bedroom apartments.
Midgard saw off bids from McLaren and United House Group to take the job, which will involve managing all activities from the pilings through the concrete frames to the fit-out and handover.
The Ruskin Square development is a former commercial high rise office site,
but has been remediated by the developer to give a flat brownfield site.
Phase 1 will see only the north eastern corner of the 9-acre Croydon Gateway site developed next to East Croydon Railway station.
The completed development, designed by Foster + Partners and AHMM will include five buildings with up to 625 homes, 240,000 sq ft of offices, retail units and a car park.
It is a major coup for the JRL Group, which over two decades has grown from grown from a company specialising in sub and superstructure packages to a business incorporating six firms to offer an integrated construction service.